Are there any significant differences between blocks in Ruby vs Groovy?

Question

I use blocks in Ruby and would like to use them in Java. Groovy seems to offer a similar feature but I do not know enough about Groovy to understand whether there are any significant differences in syntax and functionality.

Is a Ruby block equivalent to a Groovy block?

Answer 1

Not 100%. Ruby blocks require you to name all your parameters (as far as I know). A block in Groovy that doesn't specify parameters has one implied parameter, it.

Answer 2

A block is in a sense just an anymonous function. I have never programmed java, but here are some code samples for other languages to show you that blocks are similar to passing anonymous functions.

Ruby:

def add_5
  puts yield + 5
end

add_5 { 20 }
# => 25

Javascript:

var add_5 = function(callback){
  return callback.call() + 5;
}

add_5(function(){ return 20 });
// returns 25

Lua:

local function add_5(callback)
  print(callback() + 5);
end

add_5(function()
  return 20;
end)
-- returns 25

In other words, if Java supports anonymous functions like that, you got yourself a block! As they're functions, they can take arguments, just like blocks. Here's another Lua example:

local function add_something(callback)
  callback(5 / 2);
end

add_something(function(a)
  print(a + 5);
end)
-- 7.5